(C)

(D)

**Figure 6.** *Cont*.

(E)

**Figure 6.** *Cont*.

(F)

Figure 6. The influence of coating treatments on (A) total viable count (TVC) (log10 CFU/g), (B) psychotropic count (PTC) (log10 CFU/g), (C) Enterobacteriaceae (log10 CFU/g), (D) E. coli (log10 CFU/g), (E) Pseudomonas fluorescens (log10 CFU/g), (F) lactic acid bacteria (LAB) (log10 CFU/g), and (G) yeasts and molds (log10 CFU/g) in mackerel tuna fillet samples during storage at 2 °C for 20 days. Control: Uncoated mackerel tuna fillet samples (soaked samples in sterile distilled water). XAN-EEP 0%: Coated samples with xanthan containing (0%) ethanolic extract of propolis. XAN-EEP 1%: Coated samples with xanthan containing (1%) ethanolic extract of propolis. XAN-EEP 2%: Coated samples with xanthan containing (2%) ethanolic extract of propolis. a–d: Within a column, different superscripts indicate significant differences (p < 0.05). **Figure 6.** The influence of coating treatments on (**A**) total viable count (TVC) (log<sup>10</sup> CFU/g), (**B**) psychotropic count (PTC) (log<sup>10</sup> CFU/g), (**C**) Enterobacteriaceae (log<sup>10</sup> CFU/g), (**D**) E. coli (log10 CFU/g), (**E**) *Pseudomonas fluorescens* (log10 CFU/g), (**F**) lactic acid bacteria (LAB) (log<sup>10</sup> CFU/g), and (**G**) yeasts and molds (log<sup>10</sup> CFU/g) in mackerel tuna fillet samples during storage at 2 ◦C for 20 days. Control: Uncoated mackerel tuna fillet samples (soaked samples in sterile distilled water). XAN-EEP 0%: Coated samples with xanthan containing (0%) ethanolic extract of propolis. XAN-EEP 1%: Coated samples with xanthan containing (1%) ethanolic extract of propolis. XAN-EEP 2%: Coated samples with xanthan containing (2%) ethanolic extract of propolis. a–d: Within a column, different superscripts indicate significant differences (*p* < 0.05).

### 2.3.2. Psychotropic Count (PTC) 2.3.2. Psychotropic Count (PTC)

Among the major pathogens of microbial spoilage of refrigerated fish fillets are psychotropic bacteria [45]. Changes in the PTC of fish fillets are shown in Figure 6B. PTC of mackerel tuna fillets increased progressively (p < 0.05) from initial values of 2.11, 2.17, 2.15, and 2.22 log10 CFU/g to final values of 10.44, 7.88, 5.99, and 5.34 log10 CFU/g for control, XAN-EEP 0%, XAN-EEP 1%, and XAN-EEP 2%, respectively. The results depicted that the composite edible coating formed from xanthan and ethanolic extracted propolis significantly (p < 0.05) inhibited the growth of the total psychotropic bacteria. Among the major pathogens of microbial spoilage of refrigerated fish fillets are psychotropic bacteria [45]. Changes in the PTC of fish fillets are shown in Figure 6B. PTC of mackerel tuna fillets increased progressively (*p* < 0.05) from initial values of 2.11, 2.17, 2.15, and 2.22 log<sup>10</sup> CFU/g to final values of 10.44, 7.88, 5.99, and 5.34 log<sup>10</sup> CFU/g for control, XAN-EEP 0%, XAN-EEP 1%, and XAN-EEP 2%, respectively. The results depicted that the composite edible coating formed from xanthan and ethanolic extracted propolis significantly (*p* < 0.05) inhibited the growth of the total psychotropic bacteria.

#### 2.3.3. Enterobacteriaceae 2.3.3. Enterobacteriaceae

Based on previous studies, Enterobacteriaceae were found to be among the main spoilers in rainbow trout fillets stored at 4 °C [52]. The initial count of Enterobacteriaceae was 2.12 log10 CFU/g on trout fillets coated under fridge temperature [47,53]. After 15 storage days, Enterobacteriaceae counts reached 4.04, 5.19, 6.44, and 7.18 log10 CFU/g in the XAN-EEP 2%, XAN-EEP 1%, XAN-EEP 0%, and control fillets, respectively (Figure 6C). Moreover, according to the studies done by Volpe et al. [53], Bazargani-Gilani et al. [44], steady growth in Enterobacteriaceae was observed for refrigerator-stored trout chips. The findings of these studies are consistent with what was revealed by our study of the ability of coating with XAN and EEP to reduce the growth rate of Enterobacteriaceae in fillets (p < 0.05) compared to the uncoated samples (control samples) during cold storage. The Based on previous studies, Enterobacteriaceae were found to be among the main spoilers in rainbow trout fillets stored at 4 ◦C [52]. The initial count of Enterobacteriaceae was 2.12 log<sup>10</sup> CFU/g on trout fillets coated under fridge temperature [47,53]. After 15 storage days, Enterobacteriaceae counts reached 4.04, 5.19, 6.44, and 7.18 log<sup>10</sup> CFU/g in the XAN-EEP 2%, XAN-EEP 1%, XAN-EEP 0%, and control fillets, respectively (Figure 6C). Moreover, according to the studies done by Volpe et al. [53], Bazargani-Gilani et al. [44], steady growth in Enterobacteriaceae was observed for refrigerator-stored trout chips. The findings of these studies are consistent with what was revealed by our study of the ability of coating with XAN and EEP to reduce the growth rate of Enterobacteriaceae in fillets (*p* < 0.05) compared to the uncoated samples (control samples) during cold storage. The lowest number of

Enterobacteriaceae communities was found in XAN-EEP 2% fillet samples, followed by XAN-EEP 1% and XAN-EEP 0%.

As mentioned by Jalali et al. [54], *Escherichia coli* O157:H7 is the major member of Enterobacteriaceae found in the chilled silver carp flesh. The initial count of *E*. *coli* O157:H7 ranged from 2.11 to 2.21 log<sup>10</sup> CFU/g. After 20 storage days, *E*. *coli* O157:H7 counts reached 4.48, 5.15, 5.88, and 6.61 log<sup>10</sup> CFU/g in the XAN-EEP 2%, XAN-EEP 1%, XAN-EEP 0%, and control fillets, respectively (Figure 6D). A previous study showed that propolis extracts can be considered natural preservatives. Their efficacy has been proven to inhibit *Escherichia coli* bacteria in vitro due to the polyphenol compounds that propolis extracts contain, which are known for their antimicrobial effect. Among these phenolic compounds is gallic acid, known for its antibacterial activity [55]. Phenolic compounds act on the bacterial cell membrane, interfere with nucleic acid synthesis, inhibit bacterial metabolism, coagulate cytoplasmic proteins, and interfere with biofilm formation [56].
